Millions of objects, made of various materials, including, wood, stone, glass, metal, cement and brick are engraved each year. Perforation and Engraving perforation methods are disclosed in U.S. Pat. No. 4,612,737 to Adee et al. and U.S. Pat. No. 4,430,416 to Goto et al. Mechanical engraving processes typically involve the use of drilling, cutting, laser burning or sandblast engraving procedures. The majority of mechanical engraving is done with the use of resist stencils, fillers and sandblast engraving processes. Numerous abrasive materials can be used in sandblast engraving processes, including, steel shot, silicon carbide, and aluminum oxide. Typically, a sheet material capable of becoming a resist stencil is adhesively affixed to the surface of an article to be engraved. During the engraving process, the stencil covers part of the surface being engraved and protects the covered surfaces from the abrasives used for frosting the object's surface and engraving lettering and designs into the object's surface. Frosting removes the polish from the object's surface which imparts contrast and texture to the surface. Frosting is also referred to as dusting or steeling.
Flat carved designs are designs which are created to an even depth by engraving flat lines to create all images of the design. Shape carving or engraving is used to create, for example, leaves, flowers and other designs that are shaped or sculpted to resemble lifelike images. Fine shaping nozzles are used to sculpt these images to varied depths and realistic shapes. Those skilled in the art know that the formation of sculpted or shaped areas can be accomplished prior to sinking the lines to be sunk of the engraved object. Sculpting or shaping imparts a three dimensional appearance to the engraved object because the sculpting or shaping is done below the plane of the surface of the engraved object.
Generally a resist stencil itself is adhesively backed. Depending on the texture of the surface being engraved, a filler, which is brushed, sprayed or otherwise applied directly to the surface of the object to be engraved, may be required to ensure uniform adhesion of the resist stencil during the engraving process. Prior to application of the filler, the object's surface must be clean and dry, i.e., free of particulates, fine dust and moisture. Further, in some engraving processes, a filler which has an adhesive component may be necessary for proper adhesion of the resist stencil to porous, rough, or frosted surfaces. In the absence of these fillers, the resist stencil may be lifted away from the object's surface during the engraving process. Stencil lifting can result in damage to polished or frosted surfaces and destroy or create an inferior quality of the lettering and designs on the engraved object. The use of additional fillers, including adhesive fillers, during the engraving process avoids these problems.
Currently, after the engraving process, virtually every engraved object must be mechanically scrubbed to remove these fillers. Until recently, all fillers were removed from engraved surfaces by mechanical scrubbing in conjunction with the use of caustic solvent cleaners, such as, citrus cleaner or naphtha. After scrubbing with the caustic solvent cleaners, each engraved object must then be washed with soap and water to remove any remaining cleaning solvent residue. Inadequate removal of either the fillers or the caustic solvent cleaners results in staining and discoloration of the surface of the engraved object.
Recently, water soluble fillers have been developed which circumvent the necessity of using caustic solvent cleaners during the mechanical scrubbing process. However, these fillers must still be removed from the engraved surface with mechanical scrubbing and washing with water.
Alternative engraving processes have attempted to avoid the necessity of mechanically scrubbing the engraved surface to remove the fillers. However, these alternatives have been met with limited success. For example, it has been found that engraving processes which use 3M Scotch.RTM. Brand adhesive transfer tape, product number 465, as an adhesive filler, in conjunction with a resist stencil, alleviate the necessity of mechanically scrubbing the engraved surface after engraving processes performed on square or rectangular objects. Specifically, the 3M Scotch.RTM. Brand adhesive transfer tape adhesive filler is applied to the back of the stencil. Any overlapping edges of the adhesive transfer tape are then trimmed from the stencil edges. Trimming is necessary to avoid the formation of an adhesive web structure that is virtually impossible to remove. Oftentimes the adhesive web is formed during the trimming process itself. After trimming, the stencil is then applied to the surface of the square or rectangular object to be engraved. After the stencil is positioned properly and rolled or pounded into place, the square or rectangular article is carved, etched or engraved. Following engraving, the stencil is removed from the engraved surface which simultaneously removes the adhesive filler. The usefulness of this particular adhesive filler is very limited because it cannot be removed from randomly shaped objects or randomly shaped designs without the formation of an adhesive web structure that is impossible to remove from the engraved object. Specifically, this adhesive filler can only be used in conjunction with the engraving done on square or rectangular surfaces that do not include complex or randomly shaped designs.
Another engraving approach which eliminates the necessity of mechanically scrubbing the engraved surface uses a resist stencil and a non-adhesive filler. Specifically, the non-adhesive filler is applied to the object to be engraved, followed by application of the resist stencil over the filler. After the stencil is positioned properly and rolled or pounded into place the article is carved, etched or engraved. After the object is engraved the stencil is removed, wadded into a ball and aggressively rubbed over the engraved surface to remove the filler. During the aggressive rubbing process the filler sticks or tacks to the stencil surface and is removed from the engraved surface. However, this approach is only useful in engraving processes involving small surface areas, such as, for example, engraving name plates.
Since it is virtually impossible, in most engraving processes, to avoid the use of additional fillers, the removal of the filler by mechanical means from an engraved surface continues to be problematic.
In view of the prior art considered as a whole at the time the present invention was made, it was not obvious to those of ordinary skill in the pertinent art how these problems could be overcome.